Method and apparatus for making hollow rubber articles



1,639,430 Aug 36 i927' J. R. GAMMETER METHOD AND APPARATUS FOR MAKINGHOLLOW RUBBER'ARTICLES Filed March 20. 1924 Il JJM NWA '36 fnl/enjoy'John ezmmefeff Hij mama Aug. 16, 1921.

UNITED STATES JOHN R. GAmTRR, Ol AKRON, OHIO, SIGNOR T THE B. I'.GOODRIOH Ol' HRW YORK, N. Y., A CORPORATION 0F NEW YORK.

-1,639,43o PATENT oFFlcl-z.

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IETHOD AND APPARATUS 'IOR IAKING HOLLOW RUBBER ARTIOLRB.

Application led latch 20, 1924. Serial lo. 700,518.

This invention relates to the manufacture of hollow rubber articles, andmore partlcularly imperforate, hollow, rubber balls or the likecontaining air or a gas at superatmospheric ressure, as in the case ofchild'- rens play ba ls or tennis balls, for example.

To prevent a. formed, hemi-spherical blank of lastic material, such asunvulcanized rubber, from being dislodged from l0 the female die or moldas the male die is Withdrawn, and to hold the blank in the mold afterthe male die is withdrawn, 1t heretofore has been common practlce toapply suction to the mold cavit and suction i5 also has sometimes beenemp oyed to draw the material into the cavity. Another expedient hasbeen to preform the blanks, insert them in suitable mold sections, andthen bring the latter together to unite the blanks` as a hollow article.Semi-curing of the formed parts revious to assembling, to cause them tolie snugly in the mold, also has been resorted to. All of Suchmethode,however, are relatively expensive.

My chief object is to provide a method and apparatus whereby theforming, assemblmg,

and iniiating of the articles may be morev economically accomplishedthan heretofore. A more specic object is tu provide improved apparatusand procedure whereby the constituent parts of the article may be formedfrom flat sheets of plastic material which have not previously beenshaped or formed, such parts retained within their v forming molds ordieswithout the speclal application of suction for this purpose, andthen united in a chamber containing air or other gas at su r-atmosphericpressure, and then vulcanize in the mold parts in which the areoriginally formed. v

gf the accompan ing drawings:

Fi 1 is a side e evation of apparatus for forming the respective halvesof a lhollow ball, in accordance with my invention, and

the work therein, part being broken away and in section.

Fig. 2 is a view in section and elevation of a pressure chamber and theapparatus ofy Fi 1 therein.

i 3 is an elevation of a air of the mold mem rs closed and clampe uponthe work, and ready for the vulcamzer. f

Fig. 4 isa view of the finished article. Referring to the drawing, theappara- `tus comprises a U-shapedsupport or mold mold section an frame10 and a preferably cylindrical mold section 12 mounted, withsubstantial clearance, between the legs 11, 11 thereof. The,v moldcavlty therein, 13, is surrounded by a flat-faced `cutting fiange '14formed on the having its up er face in ahgnment with the top faces o theframe legs, sald face being adapted to have the stock pressed firmlythereon to form a seal,

without initially severing the stock. The frame legs are formed at theirbase with external, slotted, attachment lugs 17, 17, and at thelr upperends withvlaterally extending, undercut, wedgeshaped clamping lugs 18,18, adapted to be engaged by a drift key such as 1s .shown at 18 in Fig.3. rlhe top faces of said frame legs 11 are provided with theusualdowels and dowel apertures 19, 20 respectlvely.

The mold section 10 is adapted to be mounted upon'the table of asultable'press (not shown), to the reciprocating head of Whlch 1ssecured a die-support 21 having a dowel aperture 22 and dowel 23 adaptedto register with com lemental parts of the mold frame 10, andp having ahemi-spherical die 24 extending downwardly from its center and adaptedto enter the mold cavity 13 to shape therein a sheet of plastic,unvulcanized rubber 25 positioned over said cavity and resting upon thecutting edge 14 surrounding the same, the die support 21 being formedwith bosses 21, 21* adapted to abut the respective le 11 of the moldframe 410 to prevent the ange 14 from severing the stock in the closingof the press, but to permit the'stock to be pressed against the angetotflprm a tight fluid seal ofthe stock therew1 The die 24 is formedwith an axial bore 26 95 (Fig. 1) communicating with a source ofpressure uid through a pi e 27 mounted on the support 21, and in saibore is mounted aloose-tting plunger 28, supported and permitted limitedaxial movement therein by means of a transverse pin 29 extending throughthe upper end portion of its structure and into a` slot 30 at each sidethereof formed in the attaching stem of the die. The lower end of theplunger 28 is formed with 'a .ared, spherically convex head 31 adaptedto seatin a complemental flared end portion of the bore 26, so that whenit is so seated the die will present a smooth, uninterrupted surface tothe work. The 1mv plun er 28 is suliiciently loosefitti ng to permit t epassage of a fiuld about 1t through the bore 26. t

For uniting the two halves of the artlcle in an atmosphere of compresseda1r or other desired medium under pressure, I provlde suitable apparatusincluding a stationary, upper platen 32, a vertlc'ally movable lowerplaten 33, and a vertically movable, openended, tubular casing 34,adapted to be telescoped with the upper, stationary platen 32 and torest upon the lower platen 33, a gasket 35 on the upper platen sealing1t a amst the inner surface of the casin 34, an a gasket 36 on the loweredge of t e casing, sealin the latter to the lower platen 33. Saiplatens and casing are thus adapted to be readily assembled to provide afiuld-tlght chamber. A supply pipe 37 extends through the wall of thecasing, for introducing Huid under pressure into said chamber.

rlhe lower face of the upper platen 32 is provided with a pair ofspaced-apart, L- shaped supporting brackets 38, 38 adapted to supportand position one of the mold sections 10 in inverted position, by enagement with its respective lugs 17, and t e lower platen 33 has its topface provided with suitably positioned studs 39, 39 for positioning asimilar mold section 10, in upright position, by engagement with theslots in the respective lugs 17 at each of its ends.

For convenience, I have shown and described a single cavity mold andsingle die, but I do not limit myself thereto, as it will; be obviousthat m'y apparatus is equally applicable where multiple-cavity molds anda plurality of dies are used.

In the manufacture of balls by this apparatus, 1 first place a sheet ofunvulcanized rubber stock of the required gauge over the cavity 13 afterwhich the die 24 is moved .downward into engagement therewith to presssaid sheet into said cavity to form a heini-spherical blank, andretracted. Before the die 24 is retracted, pressure fluid, preferablyair, is admitted through the pipe 27, so that as the die is withdrawnthe plunger 28, impelled by the pressure fluid, remains momentarily incontact with the work, pressing its central portion against the mold,while the pressure fluid, issuing from the bore 26, about the plunger,breaks the seal between the die and the stock and effects separation ofthe two. The blank being pressed and thus sealed against the flange 14,is retained in the mold by its own suction, which is to say by theatmospheric pressure alone on its y exposed face.

Two such mold sections with their cavities thus lined with unvulcanizedrubber are then mounted on` the respective upper and v4lower platens,32, 33 of a suitable press, as shown in Fig.y 2, the casing 34 beingsucientl raised to permit it, and if desired, a sma ed ball may quantityof a suitable substance, such as water, may be placed in the lower blankto increase the internal pressure of the article during vulcanization.The casing is then lowered until it rests u on the lower platen, thusforming a fluid-tig t chamber, and compressed air or other suitable gasis admitted to said chamber through the supply-pi e 37.

The lower platen 33 is then raised, c osing the mold sections towardeach other until the margins of the rubber hemispheres therein arebrought forcibly together, and their outwardly-turned marginal portionspressed between the respective cutting edges 14, which seal together andsubstantially sever the same. The uniting of the two halves of thearticle entraps a quantity of the lliid under pressure in the chamber,so that the finished ball will have a corresponding internal pressure.

The ressure within the chamber is then release and the casing 34 raisedto give access to the mold, and the drift keys 18 are applied to lockthe mold sections in closed relation. The platen 33 is lowered, theassembled mold removed, and the surplus rubber, substantially severed bythe cutting flanges 14, may be removed. The mold is then placed in asuitable vulcanizer and the article therein vulcanized in the usualmanner, after which any fin or rand on the moldbe removed by anysuitable means, leaving the finished ball as shown in Fig. 4.

The tubular casing 34 is not subjected to air pressure tending stronglyto move it in an axial direction, wherefore it does not require to bepermanently secured to either of the other two members with which itencloses the pressure chamber, and this provides for easy and readyhandling of these parts to open vand close the chamber and to provideaccess for mounting and removing the mold sections.

Modifications may be resorted to within the scope `of my invention, andI do not wholly limit m cedure describe or the specific constructionshown.

I claim:

1. The method of forming and retaining.

plastic sheet material within a mold cavity which comprises pressingsaid material into conformity with said cavity, and holding it thereinby mechanical pressure at a central part of its area while withdrawingthe pressing means from another part of its area.

2. The method of forming and retaining plastic material within a moldcavity, which comprises pressinga sheet of lsaid material intoconformity with said cavity, and then forcing fluid under pressurebetween said material and the presser member as the latter is withdrawn.

3. The method of forming and retaining plastic material `within a moldcavity, which comprises pressing a sheet of said material intoconformity with said' cavity, and then forcing -iuid under pressurebetween said material and the presser member', and applying mechanicalpressure upon a portion of said material as said presser memberwithdrawn.

4. In apparatus for forming hollow ar-- ticles, the combination of amold section formed with a cavity, a. movable die aligned with thelatter and adapted to cooperate therewith to form a piece of plasticmaterial and means carried by said die and adapted to remain temporarilyin contact with the formed material as said die is withdrawn, to

.prevent displacement of said material.

5. In apparatus for forming hollow articles, the combination of a moldsection formed'with a cavity, a die aligned with the latter and adaptedto form a piece of plastic material therein, said'die beingformed withan axial bore, a plunger in said bore, and means for urging saidplunger'against the work as said die is withdrawn therefrom.

6. In apparatus for forming hollow articles, the combination of a moldsection formed with a cavity, a die aligned with said cavity and adaptedto press a sheet' of plastic material into conformity therewith, saiddie being formed with an axial bore, a plunger in said bore,'means forurging said plunger Yagainst the work as said die is withdrawn, andmeans forwithdrawing .said plunger after said die has withdrawn adeterminate distance.

7. In'apparatus for forming hollow varticles, the combination of a moldsection formed with a cavity, a die aligned with said cavity and adaptedto press a sheet of material into conformity therewith, said die beingformed with an axial bore, and means for injecting Huid under pressurethrough said bore into contact with -the work.

8. In apparatus for forming hollow articles, the combination of a moldAsection formed with a cavity, a die aligned therewith and adapted topress a sheet of plastic material into said cavity, said die beingformed with an axial bore, 4a loose-fitting plunger mounted therein, andmeans for' with and formed with an axial bore, a loosefitting plungermounted in said `bore and formed with an end face adapted to lieilushwith the face of said die, and means for applying a pressure fluid tothe opposite end of sald 'bore 'to urge said plunger toward projectedposition, said bore being adapted to permit the passage of Huidtherethrough about said plunger.

10. In apparatus for making imperforate hollow articles, the combinationof a, pair of mold sections adapted, upon being brought together, tounite two hollow blanks of plastic material'contained in theirrespective cavities, press members adapted to .force said mold sectionstogether, and means for confnin pressure fluid about said mold sectionsas tiey are thus closed, said means comprising a tubular structureadapted to be telescoped with one of said press members and to seat onthe other, and means for sealing said tubular structure against therespectivepress members. y

11. The method of making a hollow article of plastic material whichcomprises molding it between a female mold member and a male die memberand injecting Huid between the latter and the article so as to break thesuction between the two and leave the article held in the female moldmember by its own suction.

In wit-ness whereof I have hereunto set my hand this 18th day of March,1924.

JOHN R.' v

